The Two-Component System AgrAC Displays Four Distinct Genomic Arrangements That Delineate Genomic Virulence Factor Signatures.

Two-component systems (TCSs) consist of a histidine kinase and a response regulator. Here, we evaluated the conservation of the AgrAC TCS among 149 completely sequenced strains. It is composed of four genes: . We found that: (i) AgrAC system () was found in all but one of the 149 strains, (ii) the positive strains were further classified into four types based on AgrD protein sequences, (iii) the four types not only specified the chromosomal arrangement of the genes but also the sequence divergence of AgrC histidine kinase protein, which confers signal specificity, (iv) the sequence divergence was reflected in distinct structural properties especially in the transmembrane region and second extracellular binding domain, and (v) there was a strong correlation between the type and the virulence genomic profile of the organism. Taken together, these results demonstrate that bioinformatic analysis of the locus leads to a classification system that correlates with the presence of virulence factors and protein structural properties.